Mosaic printing head

ABSTRACT

A mosaic printing head for a line-dot printing system. A plurality of punch rods project through magnetic cores of a series of electromagnets and are fixedly connected to the armatures of such electromagnets. The total lengths of all rodarmature units are preferably equal. A single abutment, preferably spheroidal, locates the initial position of all rodarmature units. The normal spacing of the armature from the magnetic core in its initial de-energized, position is preferably slightly greater than the stroke of the rod-armature unit.

United States Patent [191 Moser 1 Mar. 19, 1974 MOSAIC PRINTING HEAD [75] Inventor: Erich Moser,Deisenhofen.

Germany [73] Assignee: Flrma RENA Buromaschinenfabrick GmbH & Co., Munchen, Germany [22] Filed: Apr. 20, 1971 [21] Appl. No.1 135,614

[30] Foreign Application Priority Data Apr. 24 1970 Germany ..70l5426 [52] US. Cl. 197/1 R, 101/93 C [51] Int. Cl B41j 3/10 [58] Field of Search 197/1; 101/93 C [56] References Cited- UNITED STATES PATENTS 3,108,673 10/1963 Green 197/1 R 3,333,667 8/1967 Nordin... l. 197/1' R Paige 197/1 R 3,584,575 6/1971 Distl 197/1 R 3,627,096 12/1971 Finnegan 197/1 R 3,690,431 9/1972 Howard 197/1 R Primary Examiner-Edgar S. Burr Attorney, Agent, or Firm-Woodhams, Blanchard &

Flynn [57] ABSTRACT A mosaic printing head for a line-dot printing system. A plurality of punch rods project through magnetic cores of a series of electromagnets and are fixedly connected to the armatures of such electromagnets. The total lengths of all rod-armature units are preferably equal. A single abutment, preferably spheroidal, locates the initial position of all rod-armature units. The normal spacing of the armature from the magnetic core in itsinitial'de-energized, position is preferably slightly greater than the stroke of the rodarmature unit.

8 Claims, 2 Drawing Figures MOSAIC PRINTING HEAD The invention relates to a mosaic printing head with a number of printing rods each driven by an electromagnet, which printing rods are guided at their printing ends in a mouthpiece and their other ends are rigidly connected to the armatures of the electromagnets. All of said armatures cooperate with a single abutment to determine the initial position of the printing rods.

ln the case of known mosaic printing heads of this type, the printing rods are each adjusted separately for a stroke by adjustable abutments. This requires a plurality of adjusting elements and the adjusting operation is time consuming.

The purpose of the prsent invention is to produce a mosaic printing head in which the adjustment of the stroke of the printing rods is simplified and at the same time the adjusting effort is minimized.

The invention attains this purpose by providing a common abutment plate for all the armatures which plate is formed and arranged in such a manner that the stroke length is the same for all printing rods.

Since the abutment plate acts as an abutment element for all printing rods it is no longer necessary to provide as previously for individual adjustment of the strokes of the printing rods.

In order to obtain a simple shape for the abutment plate, for example a spherical cup, according to a further feature of the invention the length between the printing end of the printing rod and the outer end of the armature is the same for all printing rods and the abutment plate forms the geometric determinant for the outer ends of all armatures in the initial, i.e. rest position of the printing rods. In other words, the abutment plate determines the outer limiting position of the armatures in relation to the geometry of their alignment.

In addition, there is obtained through this invention the manufacturing advantage that it is here possible to make all printing rods of equal length. Individual adjustment of the lengths of the printing rods thus is not required.

In order to obtain uniform driving force and consequently uniform stroke speeds, according to a further characteristic of the invention, the ends of the magnetic cores of the electromagnets cooperate with the adjacent ends of the armatures to form a work air gap, i.e. the space through which the leading end of the armature is movable during a printing stroke, and are spaced from the abutment plate a distance which is equal to the sum of stroke length and the armature length. Thus at the instant of the contact by the printing rods onto the printing surface the maximum force is applied by the electromagnet onto the printing rods because the armatures, at this instant, are at a minimum distance from the adjacent ends of the magnetic cores of the electromagnets.

Advantageously the stroke length and/or the plunging armature length is the same for all printing wires.

According to a preferred embodiment of the invention, a base member is provided which is made of a good heat-conducting metal i.e. a heat conductive metal and the electromagnets are secured to this base member. Forwardly of this base member there is arranged a guide member of a material which has good sliding characteristics for the printing rods, i.e. a low friction material. The guide member is releasably connected to the base member and a gap is formed between the mouthpiece and the guide member. This printing head structure permits a good heat dissipation when the printing head is in operation and at the same time maintains a good heat balance between electromagnets which are in operation and those which are not in operation. This largely avoids the occurrence of any unevenness in the printing face. The gap between the mouthpiece and the guide member for the printing rods permits the discharge of abrasive or other materials, as paper dust and the like. For the manufacture of the guide member it is advantageous that same is constructed separately from the base member.

According to a further feature of the invention a particularly simple construction of the printing head is obtained by fastening the abutment plate for the armatures of the electromagnets to the base member. The mouthpiece and guide member are' advantageously held in place by a removable housing of several separable parts. This permits the exchange, i.e. replacement of mouthpiece and guide member. The metallic housing parts assure in addition a good heat discharge to the surrounding atmosphere.

An exemplary embodiment of the invention is illustrated in the drawing and will be described hereinafter.

In the drawing: I

FIG. 1 is a top view of the mosaic printing head according to the invention and FIG. 2 is a cross sectional view along the line IIII of FIG. 1.

The mosaic printing head 1 which is guided and held for writing in a manner not illustrated consists of the base member 2 of a good heat-conducting metal, preferably aluminum. Electromagnets 3 are secured to said base member and in this embodiment are arranged in seven stacks of five in each stack. The electromagnets 3 consist of the magnetic core 4, which is pressed at its end 5 into the base member 2. The magnetic coil 6 is fixedly secured around the magnetic core 4 and an armature 7 enters into the magnetic coil 6. The armature is biased outwardly by a return spring 8. A printing rod 9 is rigidly connected tothe armature 7, which printing rod is guided in a small bore through the magnetic core 4.

A guide member 10 is positioned in front of the base member 2, which guide member is provided with guide channels for the printing rods 9. A mouthpiece 12 consisting of a material of good sliding characteristics, i.e. a low friction material is positioned in front of the guide member 10 and spaced therefrom by the gap 11. The mouthpiece 12 has also guide channels for the printing rods. The front ends of the printing rods strike a printing surface 13 when the electromagnets 3 are energized and the corresponding armatures 7 are drawn inwardly.

Webs 14 are secured to the base member 2, with which webs the abutment plate 15 is connected, for ex ample by means of screws 16. The abutment plate 15 exactly determines the initial position of the rear ends 17 of the armatures. Thus the abutment plate 15 may be formed and arranged in such a manner that it locates the outer ends of all armatures on a desired geometric pattern in the initial position of the printing rods. Advantageously all printing rods 9 have the same length, the armatures 17 are also of equal length and the armatures are connected to the printing rods in such a manner that the'total length of printing rods and armatures is the same for all printing rods. With such a construction the abutment plate is in this embodiment approximately the shape of a spherical cup. The ends of the magnetic cores 4 cooperate with the armatures 7 to define therebetween the work gap, or space, 18, i.e. the stroke path of the armature, and are positioned along a line 19 which is determined by the equal stroke of the printing rods and by the equal length of the printing rods and the armatures. With this arrangement, when the electromagnet is energized and the armature 7 is thereby drawn in, the maximum force on the printing rod is obtained if the stroke of the armature is so adjusted that in its energized position, it just fails to touch the facing end of the magnetic core 4.

The printing head 1 is surrounded by a housing having separable, opposed parts 20 and 21 (FIG. 1). By making said parts of metal, there is obtained a good heat discharge to the surrounding atmosphere. The housing parts 20, 21 at the same time retain the mouthpiece 12 and the guide member 10 therewithin. The housing parts 20, 21 are secured to the base member 2 by means of screws 22.

Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications ofthe disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

l. A mosaic printing head, comprising in combination:

a plurality of printing rods;

a base member;

a corresponding plurality of electromagnets secured on said base member and arranged for driving said printing rods on a one-to-one basis, said electromagnets having armatures with exposed outer ends;

a mouthpiece for guiding said printing rods at their printing ends, the other ends of said printing rods being fixedly connected to said armatures of said electromagnets, the length from the printing end of the printing rod to the outer end of the corresponding armature being equal for all printing rods;

means defining a single, common abutment plate fixed with respect to and spaced from-said base member and opposed to and engaging the outer ends of all said armatures for simultaneously deter mining, without intervening individually positionable means, the initial position of the plurality of printing rods, said armatures and said printing rods fixed thereto extending convergently from said common abutment plate, said abutment plate being curved and being a portion of a substantially spherical cup, said abutment plate extending transversely and continuously between and past all said outer armature ends, said abutment plate being formed and located such that the stroke length is equal for all said printing rods, whereby to eliminate the need for individual adjustment of the initial position and length of the printing rods.

2. A mosaic printing head, comprising in combination:

a plurality of printing rods;

a corresponding plurality of electromagnets arranged for driving said printing rods on a one-to-one basis, said electromagnets having armatures;

a mouthpiece for guiding said printing rods at their printing ends, the other ends of said printing rods being fixedly connected to said armatures of said electromagnets, the length from the printing end of the printing rod to the outer end of the corresponding armature being equal for all printing rods;

a common abutment plate opposed to and engageable by the outer ends of all said armatures and simultaneously determining the initial position of the plurality of printing rods, said abutment plate being formed and located such that the stroke length is equal for all said printing rods, whereby to eliminate the need for individual adjustment of the initial position and length of the printing rods, said electromagnets each including a magnetic core, the ends of the magnetic cores of the electromagnets cooperating with the adjacent ends of the armatures to form in each case a space into which the armature is movable;

a heat conducting base member spaced intermediate said mouthpiece and abutment plate, webs extending from said abutment plate to said base member for fastening the abutment plate to the base member, the base member and abutment plate being correspondingly curved, said cores being pressed into said base member and extending radially therefrom toward said abutment plate, said electromagnets each including a coil, each said coil being fixed on its corresponding core and spaced axially from said base member and abutment plate.

3. A printing head according to claim 2 in which the armatures and the printing rods fixed thereto extend convergently from the common abutment plate, the curvature of said abutment plate corresponding to such convergence of said armatures, said abutment plate ex tending transversely between and past said outer armature ends.

4. A printing head according to claim 2, in which said magnetic cores being spaced from the abutment plate by a common distance, the sum of stroke length and armature length for each armature being equal to said common distance.

5. A printing head according to claim 4, in which said common abutment plate is a portion of a substantially spherical cup.

6. A printing head according to claim 2, including a base member of heat-conducting material, the electromagnets being secured to said base member, and further including a guide member of low friction material positioned in front of and releasably connected to said base member for guiding said printing rods, said mouthpiece being spaced in front of said guide member for defining a gap therebetween.

7. A printing head according to claim 6, in which the electromagnets each include a magnetic core secured on the base member, said abutment plate being secured to said base member in spaced relation thereto and to said cores.

8. A printing head according to claim 6, including a removable housing having separable opposed parts fixable with respect to said base member in surrounding relation to said printing head, said mouthpiece and guide member being perimetically surrounded and held in place by said housing. 

1. A mosaic printing head, comprising in combination: a plurality of printing rods; a base member; a corresponding plurality of electromagnets secured on said base member and arranged for driving said printing rods on a one-toone basis, said electromagnets having armatures with exposed outer ends; a mouthpiece for guiding said printing rods at their printing ends, the other ends of said printing rods being fixedly connected to said armatures of said electromagnets, the length from the printing end of the printing rod to the outer end of the corresponding armature being equal for all printing rods; means defining a single, common abutment plate fixed with respect to and spaced from said base member and opposed to and engaging the outer ends of all said armatures for simultaneously determining, without intervening individually positionable means, the initial position of the plurality of printing rods, said armatures and said printing rods fixed thereto extending convergently from said common abutment plate, said abutment plate being curved and being a portion of a substantially spherical cup, said abutment plate extending transversely and continuously between and past all said outer armature ends, said abutment plate being formed and located such that the stroke length is equal for all said printing rods, whereby to eliminate the need for individual adjustment of the initial position and length of the printing rods.
 2. A mosaic printing head, comprising in combination: a plurality of printing rods; a corresponding plurality of electromagnets arranged for driving said printing rods on a one-to-one basis, said electromagnets having armatures; a mouthpiece for guiding said printing rods at their printing ends, the other ends of said printing rods being fixedly connected to said armatures of said electromagnets, the length from the printing end of the printing rod to the outer end of the corresponding armature being equal for all printing rods; a common abutment plate opposed to and engageable by the outer ends of all said armatures and simultaneously determining the initial position of the plurality of printing rods, said abutment plate being formed and located such that the stroke length is equal for all said printing rods, whereby to eliminate the need for individual adjustment of the initial position and length of the printing rods, said electromagnets each including a magnetic core, the ends of the magnetic cores of the electromagnets cooperating with the adjacent ends of the armatures to form in each case a space into which the armature is movable; a heat conducting base member spaced intermediate said mouthpiece and abutment plate, webs extending from said abutment plate to said base member for fastening the abutment plate to the base member, the base member and abutment plate being correspondingly curved, said cores being pressed into said base member and extending radially therefrom toward said abutment plate, said electromagnets each including a coil, each said coil being fixed on its corresponding core and spaced axially from said base member and abutment plate.
 3. A printing head according to claim 2 in which the armatures and the printing rods fixed thereto extend convergently from the common abutment plate, the curvature of said abutment plate corresponding to such convergence of said armatures, said abutment plate extending transversely between and past said outer armature ends.
 4. A printing head according to claim 2, in which said magnetic cores being spaced from the abutment plate by a common distance, the sum of stroke length and armature length for each armature being equal to said common distance.
 5. A printing head according to claim 4, in which said common abutment plate is a portion of a substantially spherical cup.
 6. A printing head according to claim 2, including a base member of heat-conducting material, the electromagnets being secured to said base member, and further including a guide member of low friction material positioned in front of and releasably connected to said base member for guiding said printing rods, said mouthpiece being spaced in front of said guide member for defining a gap therebetween.
 7. A printing head according to claim 6, in which the electromagnets each include a magnetic core secured on the base member, said abutment plate being secured to said base member in spaced relation thereto and to said cores.
 8. A printing head according to claim 6, including a removable housing having separable opposed parts fixable with respect to said base member in surrounding relation to said printing head, said mouthpiece and guide member being perimetically surrounded and held in place by said housing. 